The purpose is to evaluate the performance of an implantable hand grasp neuroprosthesis designed to restore grasp and release in the paralyzed hand of high-level spinal cord injury patients (C5 and C6 tetraplegics) through the application of functional neuromuscular stimulation (FNS). The device enables these patients to acquire and manipulate unmodified objects that are commonly encountered in activities of daily living, thus providing them with manipulative capabilities otherwise unavailable.